Air jet spinning machines conforming to this type serve the purpose of the production of a yarn from an elongated fiber composite with the assistance of a vortex air flow generated by corresponding air nozzles within the vortex chamber. Thereby, in the area of the inlet mouth of the typically spindle-shaped yarn formation element, the outer fibers of the fiber composite are wound around the internal fibers (core), such that, as a result, a stable yarn arises, which can be ultimately led away through the draw-off channel from the vortex chamber and, with the assistance of the specified spooling device, can be spooled on a sleeve.
During the spinning process, if spinning flaws arise (thick or thin parts of the yarn, yarn tears, unsatisfactory feed of the fiber composite, etc.), or if the spinning machine is stopped for a certain period of time, a piecing process is necessary subsequent to the respective event that interrupts the production of yarn. In this case, the end on the spool side of the already produced yarn (that is, the end section of the yarn section last spooled prior to the interruption of yarn production) is fed back, counter to the actual spinning direction (which corresponds to the transport direction specified above), through the draw-off channel into the vortex chamber, and from there into the area of the inlet (or a fiber guide element placed in this area). Following the return, outside of the spinning nozzle, with the assistance of a service robot, a device on the spinning unit or manual effort, the yarn is brought into contact with the end of the fiber composite through an overlap on both sides.
Finally, the yarn end, and with it the end of the fiber composite, is moved inside the vortex chamber by switching on the air nozzles and starting the spooling device and is exposed there to the vortex air flow (whereas, at this point in time, the device delivering the fiber composite, which is preferably formed by a drafting system upstream of the spinning nozzle in the transport direction, is or was already in operation, in order to convey the fiber composite in the direction of the inlet of the spinning nozzle). The connection area or overlap area between the yarn end and the end of the fiber composite ultimately passes through the inlet mouth of the spindle. The spinning process then continues as usual; that is, the spinning unit once again operates in normal mode and produces a yarn.
While the piecing process described above has become accepted and has delivered satisfactory results in this regard, it cannot be ruled out that the connection of yarn end and the corresponding end of the fiber composite fails during the piecing process or comes loose again prior to passing through the spinning nozzle. In such an event, the piecing process must be carried out once again, possibly after a corresponding cleaning of the spinning nozzle, such that the method appears worthy of improvement with regard to its reliability.